In simulators (such as those used for aircraft pilot training), in sophisticated computer graphics, in sophisticated video games, and in television broadcast studio equipment it is desirable to retrieve pictorial information from computer memory and to electrically adjust the focus and depth-of-focus of that pictorial information. (Depth-of-focus is alternatively called depth-of-field.) One could provide for such photographic camera simulation by photographing a field of view with, practically speaking, all combinations of focal length and aperture possible with a given camera lens, converting the photographs to electric signal descriptions, and storing the electric signal descriptions in computer memory. Excessive computer memory capability is required for separately storing the hundreds of pictures with reasonably high resolution, particularly if they are in full color.
E. H. Adelson in U.S. patent application Ser. No. 611,962 filed May 18, 1984 entitled "IMPROVED DEPTH-OF-FOCUS IMAGING PROCESS METHOD", now U.S. Pat. No. 4,661,986 and assigned to RCA Corporation describes a method of generating electric signal descriptions of a field of view, with depth-of-focus extended beyond the normal capability of the camera lens. Adelson derives an improved-focus two-dimensional image from an assemblage of separately focused two-dimensional images of the same three-dimensional field of view, each of which images is sampled with the same spatial resolution in each direction in the two-dimensional image plane. These images with depth-of-focus limited by the lens capabilities are each subjected to two-dimensional spatial-frequency spectrum analysis, with each subspectrum being an octave or smaller in spatial frequency. Samples of given spatial frequency and location, each drawn from a different one of the assemblage of separately-focused 2-D images, are compared with each other to select the largest of the samples. An electric signal description of an extended depth-of-focus image is then synthesized from the selected samples. This procedure and the pyramid-based spatial-frequency spectrum analysis techniques used to implement it are explained in greater detail by J. M. Ogden, E. H. Adelson, J. R. Bergen and P. J. Burt in their RCA ENGINEER, Vol. 30, No. 5, Sept./Oct. 1985 article "Pyramid-based Computer Graphics", appearing on pages 4-15 of that publication and incorporated herein by reference.
Adelson also describes in his patent application Ser. No. 611,962 the use of two portions of computer memory mapping the same image space, the first portion storing at each location therein a full depth-of-focus sample of the image and the second portion storing the distance of the principal axis of the camera lens from the object plane of that image sample. This image memory organization is used to implement three-dimensional microscopy.
A similar image memory organization, the present inventor points out, allows for the efficient storage of all the information necessary to re-create with reasonable accuracy the hundreds of photographs of a field of view taken with (practically speaking) all combinations of focal length and optical aperture possible with a given camera lens. Rather than a multiplicity of similar-size portions of image memory being taken up to store electrical descriptions of respective ones of these photographs, only two portions of image memory of such size are used. The first portion of image memory stores full depth-of-focus picture element (or "pixel") samples for each of the points in two-dimensional image space. The second portion of image memory stores all the information from which one may determine, for each of the pixels in two-dimensional image space, the distance between the principal axis of the camera lens and the object plane from which the pixel is obtained.